1. Field of the Invention
The present invention relates to a system for coupling a toothed starter ring to a support connected to the output shaft of an internal combustion engine, in which system the support has a substantially cylindrical peripheral surface adapted to receive the ring and the ring has a substantially cylindrical inside peripheral surface complementary to the substantially cylindrical peripheral surface of the support and is adapted to cooperate with a rotor of a starter motor of the internal combustion engine.
2. Description of the Prior Art
The starter toothed ring is conventionally shrink-fitted, screwed or welded to its support, without leaving the ring any degree of freedom, in accordance with standard practice in the gearing art.
The support of the starter ring is generally the flywheel, or a member forming part of an assembly serving as a flywheel, of the internal combustion engine, and rotates with the latter.
A ring fixed to its support in this way is of satisfactory reliability. It is capable of withstanding and providing a number of engine starts of the order of 20 000 to 60 000, which is generally sufficient given the service life and average conditions of use of a vehicle.
However, starting an engine by the starter motor driving the starter ring and its support generates noise at an overall level greater than 90 decibels, and all parties involved, manufacturers and users, want a significant reduction in that level.
What is more, in the short- or medium-term, the fight against atmospheric pollution caused by the operation of internal combustion engines runs the risk of imposing the xe2x80x9cstop/go,xe2x80x9d practice of stopping the engine of a vehicle when the vehicle is stopped, either at a red traffic light or because of a traffic jam.
In the case of vehicles used intensively in towns, this practice runs the risk of increasing the aforementioned number by a factor of at least four to six. In this case, a starter ring would have to withstand at least 200 000 engine starts, if riot 250 000 or 300 000, and perhaps many more.
FR-A-788 061 discloses a coupling system of the aforementioned type in which the ring is slidably mounted on an annular soundproofing material facing fixed to the cylindrical peripheral surface of the flywheel. Forces are transmitted between the ring and the flywheel either by a radial rubber ring glued to respective complementary radial faces of the ring and the flywheel or by rubber fingers engaged in notches on respective cylindrical peripheral surfaces of the flywheel and the ring.
A coupling system of the above kind, in which the whole of the ring can turn on its axis relative to the flywheel, cannot increase the service life of the aforementioned conventional system and does not have the required reliability.
The objects of the present invention are to remedy the drawbacks of conventional coupling systems known in the art and to propose a coupling system of the aforementioned type in which the ring is capable of withstanding a number of engine starts corresponding to the new figures indicated hereinabove, combined if possible with a significant reduction in noise level.
The invention provides a system for coupling a starter toothed ring to the peripheral part of a support connected to the output shaft of an internal combustion engine, the support including a substantially cylindrical peripheral surface adapted to receive the ring and the ring including a substantially cylindrical inside peripheral surface complementary to the peripheral surface of the support and adapted to cooperate with a rotor of a starter motor of the internal combustion engine, the axial faces of each tooth of the ring including, if necessary, a self-lubricating coating, wherein the complementary substantially cylindrical peripheral surface of the ring is fixed over at least part of its extent to the substantially cylindrical peripheral surface of the support in such a manner that the ring can deform slightly in the radial direction toward the shaft to reduce the maximum stresses exerted on the ring during a starting operation.
Some flexibility and some possibility of radial deformation are therefore imparted to the starter ring, which goes against gearing design rules.
In a manner that is entirely surprising, this damps the effect of impact on the teeth of the ring exposed to the pressure exerted by the teeth of the rotor of the starter motor on starting the engine.
The damping effect spectacularly increases the service life of the starter ring and that of the gear, which service life can correspond to a minimum of approximately 200 000 engine starting cycles.
The noise generated by the support and the starter ring when the rotor of the starter motor meshes with the ring is also reduced by an amount of the order of 5 to 7 decibels.
Other features and advantages of the present invention will become apparent in the course of the following detailed description, which is given with reference to the accompanying drawings, which are given by way of non-limiting example only.